The present invention relates to a general service incandescent lamp, and more particularly, to a general service incandescent lamp having a light source with an enhanced temperature gradient.
Light sources containing a filament, a halogen compound along with a relatively high pressure fill-gas have relatively recently been implemented for incandescent type lamps, and provide increased light output relative to that of the common incandescent lamps filaments.
The implementation of the light source operated at a relatively high pressure must take into account the highest or maximum operating temperature which if equalled or exceeded correspondingly causes the envelope of the light source to soften, obtain a plastic-like state, deform and become inoperative. The maximum operating temperature of the envelope of the light source is determined, in part, by commonly known "hot spots" typically located directly above and at the center of the operating filament.
As the wattage desired for the incandescent lamp increases, the operating temperature of the inner envelope of the light source is increased which commonly requires an increase in the diameter of the envelope creating certain disadvantages.
One of the disadvantages of such an increase is the difficulty experienced in the pinching process in which one end of the inner envelope, having spatially disposed therein the filament and associated structural members, is pinched and sealed. Increasing the diameter of the envelope of the light source increases the mass to be pinched and sealed, which correspondingly prolongs the pinch and seal process and in certain cases hinders the attainment of a proper seal.
Increasing the diameter of the envelope may also create a problem associated with "cold spots". The "cold spots" are those locations within the inner envelope, typically in the corners of the inner envelope and at distances most remote from the operating filament, which allow the halogen compound within the confines of envelope to condense in the "cold spots" which, in turn, reduces the contribution of the halogen compound related to maintaining the desired light output of the light source.
Increasing the diameter of the envelope also increases its mass which increases the difficulty of mounting the light source within an outer envelope of the lamp in which the light source is employed. Further, the increased mass disadvantageously adds to the cost of the light source. Furthermore, the increased mass disadvantageously adds to the stored energy that may need to be contained under an unlikely rupture condition of the light source.
The present invention increases the temperature of the cold spots to acceptable levels without decreasing the diameter of the inner envelope. These acceptable levels are primarily provided by a light source having a desired inner walls temperature gradient. The light source increases the operating temperature typically experienced at the cold spot locations and thereby reduces the temperature gradient between the hot and cold spots. The present invention also provides an improved method for forming the desired light source.
Accordingly, objects of the present invention are (1) maintaining the maximum diameter of the light source while reducing the temperature gradients of the typically experienced hot and cold spots, (2) maintaining the diameter of the light source so as to facilitate the pinch and seal processes, and (3) providing a light source having a desired temperature gradient while at the same time reducing the complexity of the mounting structure of the light source within the outer envelope of the lamps employing the light source.
These and other objects of the present invention will become apparent upon consideration of the following description taken together with the accompanying drawing.